Water flow and pressure question, and how much water through wet headers?

[tonyoverthere]

Hi all. Picked up new-to-me jet boat and have a couple quick questions.

It has a 455 Olds and the Hardin 4-port thermostat kit in it. With this kit, water bypasses the engine and dumps directly overboard until the thermostat opens, then it allows water to flow through obviously, and the hot water coming out then dumps overboard. Previous owner had gate valve wide open. Should I still need to regulate water flow via the gate valve with this setup or leave it full open? Just dont want to over-pressurize the engine is all.

https://www.hardin-marine.com/p-80797-polished-stainless-thermostat-kit-for-455-olds.aspx

Next question: after the gate valve, there is a tee and another gate valve that controls water flow to the over-transom headers. Previous owner had that shut and ran the headers dry. I would like to run them wet. I believe I just crack that gate valve open very slightly, so as to only have a fine mist when above 1800 RPM, and pretty much dry below 1800 RPM. Sound about right?

Thank you!

 

[DarkHorseRacing]

The Olds may be different from a BBC but on ours we ran a pressure relief right off the water intake from the bowl and set it to like 15 psi and dumped anything higher out the back. We didn’t use a thermostat at all, just water all the time.

Boats aren’t cars, it sure what the thermostat really solves on a boat.

As for the exhaust headers, you could probably dial the water flow with a gate valve and leave it once you get it set. But the question I would ask is are the headers supposed to be run dry or did he get a leak and solve it that way?